This application is based on and claims the benefit of German Patent Application No. 198 07 076.4 filed Feb. 20, 1998, which is incorporated by reference herein.
This invention relates to a method to supply client nodes with data streams as described in the introductory portion of claim 1, a method to support the supply of client nodes with data streams as described in the introductory portion of claim 9, a data delivery system as described in the introductory portion of claim 10, and a central server node as described in the introductory portion of claim 11.
The invention is based on a video-on-demand system of the type, by way of example, that is described in EP 0696872 A2.
Such a video-on-demand system consists of a video server node which is connected by means of a communications network with a plurality of client nodes. A client node is formed by a set-top box which is connected to a television set. The video server node has a memory in which video data sets containing various content, for example different films, are stored. The video server node also has a plurality of video playback devices that play back these video sets and send the stream of video thus generated to a requesting client. The video server node also has a control unit which assigns a video playback device to a requesting client and initiates the transmission of the video data stream from the assigned video playback device to the client node. The assignment is thereby made with the objective of sending a video data stream in parallel to as many client nodes as possible.
If a client node requests the playback of a video data set with a specified content, in particular the playback of a specified video film, then it is possible that the video server node may not be able to successfully assign a playback unit. Such a situation can occur, for example, if sufficient resources are no longer available in the video server node. It is also possible that the requested video film is not even stored in the memory of the video server node, and that therefore the video server node cannot supply the requested video film. It is also possible that the entire connection capacity of the video server node is already being utilized by other client nodes, and therefore no further access to the video server nodes is possible.
The object of the invention is to improve the supply of client nodes with data streams of different content.
The invention teaches a method to supply client nodes with data streams as described in the characterizing portion of claim 1, a method to support the supply of client nodes with data streams as described in the characterizing portion of claim 9, a data delivery system as described in the characterizing portion of claim 10, and a central server node as described in the characterizing portion of claim 11.
The invention is based on the teaching that the client servers share a set of a plurality of data server nodes that are connected to the client nodes by means of a communications network. A central server node monitors these data server nodes and, by means of the data obtained, performs a dynamic assignment of client nodes to data server nodes.
The data sets, which are played back by a data server node and are sent in the form of a data stream to a client node, thereby generally contain xe2x80x9cstreamxe2x80x9d data such as video, audio or multimedia files, i.e. files that are sent in real time at a constant transmission rate to the client nodes.
The advantage of the invention is that a client node thereby obtains transparent access to the content and resources of a plurality of data server nodes. A client node can thereby have transparent access to a larger number of contents with a lower probability of rejection. As a result of the geographically distributed structure of the data server nodes, it is also possible to achieve a more uniform utilization of capacity of the communications network that transmits the data from the data server nodes to the client nodes. The architecture claimed by the invention therefore has the following advantages over the potential use of a very efficient central data server node: The risk of a spot overload of the communications network is reduced. The length of the connecting lines and thus the resources of the communications network occupied are reduced. The likelihood of failure of the data delivery system is reduced.
Above all, a data delivery system as claimed by the invention has advantages when a large number of client nodes are required to have access to a large number of different contents. Such a system is difficult to realize using the solutions of the prior art.
Advantageous configurations of the invention are described in the subclaims.
It is thereby advantageous above all that the central server nodes also centrally manage the distribution of the contents to the data server nodes. A further optimization of the data delivery system is thereby possible, and the quality of service of the data delivery system and the resources required by it are further reduced.